This invention relates to applying stretch labels to containers and other articles. It is common practice to apply labels to containers and other articles by supplying a continuous length of label material from a roll, cutting it into suitable lengths which are transferred to a rotating vacuum drum which picks up each label in turn on its cylindrical surface by means of vacuum and transports each label to a label applying station where it is wrapped around a container. For the purpose of adhering the label to the container, glue is applied to the container and/or to the label, usually the latter, at its leading end and at its trailing end. An adhesive may be formed in situ by the use of a solvent. Also, heat sealing of the overlap between the trailing end of the label of the leading end of the label may be employed.
Hereinbelow for convenience the term xe2x80x9clabelxe2x80x9d or xe2x80x9clabelsxe2x80x9d and the term xe2x80x9ccontainerxe2x80x9d will be used, but it is to be understood that other segments of sheet material may be applied, e.g., for decorative purposes and that other articles than containers may have labels or other segments of sheet material applied to them.
Such label application to containers may be carried out with a stack of precut labels rather than severing labels from a continuous length of label material.
Representative patents relating to such label application are U.S. Pat. Nos. 4,108,709; 4,108,710; 4,500,386; 5,091,040; 5,137,596 and 5,269,864. Such label application may also be carried out and is often carried out with a heat shrinkable label material which, after application to the container, is subjected to heat to cause it to shrink, e.g., into a recessed area of a container or onto contoured portions such as the neck or shoulder of a container. For example, in U.S. Pat. No. 4,704,173, such heat shrink labeling is illustrated by application of a label to a container having a cylindrical body above and below which are portions of the container which are of lesser diameter. The heat shrinking shrinks the label onto such areas of lesser diameter.
An alternative to such heat shrinking/contour labeling is the application of stretchable labels, which are stretched before application and which, after application, contract and closely adhere to the recessed and/or contoured portions of the container. An example of such stretch labeling and the method and machinery for accomplishing it is provided by Automatic Label Systems of Twinsburg, Ohio, who supply what are called xe2x80x9cAuto-Sleeve(copyright) stretch sleeve labels.xe2x80x9d By The Auto-Sleeve(copyright) labels are first formed into sleeves. The sleeves have a diameter less than the maximum diameter of the container to which they are to be fitted and the sleeve is stretch fitted over the container and when so applied it contracts and relaxes to fit the container tightly. This method avoids the need to use glue, heat or solvent to adhere the label to containers and it avoids the need to heat the label on containers to shrink the label material onto the container.
However, that method requires first forming the stretch label material into a sleeve, then fitting the sleeve over the. container.
It is an object of the present invention to provide a method and machinery which will apply stretch labels in sheet form, as for example in U.S. Pat. No. 4,500,386 or U.S. Pat. No. 4,108,709, and to apply the labels in stretched condition without the need to preform a sleeve.
The above and other objects will be apparent from the ensuing description the appended claims.
In accordance with the invention stretch label material, e.g., stretchable polyethylene is supplied continuously to a cutting instrumentality such as that shown in U.S. Pat. No. 4,181,555 and each label, after it passes through the cutter and before it is cut into an individual label is supplied to a rotating vacuum drum and its leading end is placed on the rotating vacuum drum, which grips the label by vacuum. Alternatively, but less desirably, precut labels are fed from a stack of the same to a vacuum drum, as for example in U.S. Pat. No. 4,978,416, likewise being gripped by the vacuum of the vacuum drum. In either case the peripheral speed of the drum exceeds the linear speed of the label. In the absence of a sufficiently high vacuum this would lead to slippage of the label on the drum. However, by using a sufficiently high vacuum this is avoided. Hence the label is held firmly on the drum by vacuum and by reason of the fact that the peripheral speed of the drum is greater than that of the label feed through the cutting instrumentality, the label is stretched.
Alternatively the leading end of the label may be clamped onto the vacuum drum, e.g., as described in Eder U.S. Pat. No. 5,116,452. The combined use of a clamp and a vacuum strong enough to hold the label against slippage may also be employed.
The label thus held in stretched condition on the drum is then contacted, e.g., at the leading end and at the trailing end by a glue applicator which applies glue to the leading end and to the trailing end so that when the label is wrapped around the container it is adhered thereto. Also the use of a solvent applied to the label and absorbed by the label to form an adhesive in situ may be employed. Alternatively, also heat sealing of the ends of the label together may be accomplished as for example in U.S. Pat. No. 5,137,596.
The problem of relaxation of the label from its stretched condition when it is released from the vacuum drum may be dealt with as follows: The adhesive applied to the leading end of the label to adhere it to the container may be an adhesive which bonds very quickly and strongly to the label and to the container, such that it prevents or minimizes relaxation of the label as it leaves the vacuum drum and bonds to the container. Suitable adhesives are National 4000, a product of National Starch Co. Of Chicago, Ill. and Century 7002, a product of Century Adhesives, of Columbus, Ohio. Alternatively, or in conjunction with the use of such as adhesive, the adhesive may be applied as a series of dots spaced lengthwise along the label or around the periphery of a container. Thus the first dot or array of dots of adhesive near the leading end of the label will be followed by a dot or array of dots spaced a short distance from the first dot or array, etc. Therefore the label will be held firmly on the container as each segment comes off of the vacuum drum and it is prevented from relaxing or the relaxation of the label is not significant.
Adhesive may be applied to the container rather than the label or it may be applied to both the container and the label. In U.S. Pat. No. 3,834,963, adhesive application to the container is shown. The adhesive application to the container may be (as in U.S. Pat. No. 3,834,963) applied to both the container and label, and the pattern of adhesive applied to the container may vary. For example, a line of adhesive may be applied to the container for adhesion to the leading end of the label, or it may be applied both to the leading end and to the trailing ends of the label, or it may be applied to the entire circumference of the container as a succession of dots.
Hereinabove, xe2x80x9cdotsxe2x80x9d of adhesive have been referred to and as stated in connection with application to the label, adhesive may be applied as bands or strips to the container and/or to the label.
The labeled container is then removed from the label applying equipment. That portion or those portions of the stretched label overlying a recessed surface or surfaces of the container will shrink onto the recessed portion or portions.
If there is a recessed area on the container which is of a magnitude such that the relaxation of the label will not suffice, e.g., in the case of a deep groove in a container intended as a fingerhold, a heat shrinkable label may be employed, assisted if need be by perforations overlying such deeply recessed area or areas to release air trapped between the label and the container. Heat is applied to shrink the label onto ro into such deeply recessed area or areas.
Instead of employing a greater peripheral speed of the vacuum drum to stretch the label, the container may be caused to spin at a peripheral speed which is greater than that of the vacuum drum, thereby stretching the label. The peripheral speed of the container is the composite of the speed at which it is caused to spin, its diameter and the speed at which it travels after first making contact with the label. The difference in speed of the label while on the drum and this composite speed can be governed quite precisely by gears or by computer controlled motors as described below. To prevent the label from slipping on the container due to its greater peripheral speed, an adhesive which bonds strongly and quickly may be used. Alternatively (and/or in addition to such procedure), adhesive may be applied as a succession of dots so that the label is adhered to the container, not at one point but at several points.
The label may also be stretched by both procedures, that is by operating the vacuum drum at a peripheral speed greater than the label feed and by also causing the container to spin more at a composite speed greater than the peripheral speed of the vacuum drum.